Transformer Encoder: Given the output of the linear projection, the sequence of vectors \(\mathbf {Z}_0\)  is fed to the transformer encoder [1]}. As it can be seen from Fig. REF , the transformer encoder consists of \(L\)  layers, with two modules, i.e., the Multihead Self-Attention (MSA) mechanism, and the MLP modules, where MLP module consists of two linear layers with Gaussian Error Linear Unit (GELU) activation function. The output of the MSA and MLP modules of layer \(l\) , for (\(1 \le l \le L\) ) are given by
\(\mathbf {Z}^{^{\prime }}_l &=& MSA(LayerNorm(\mathbf {Z}_{l-1})) + \mathbf {Z}_{l-1},\\\mathbf {Z}_l &=& MLP(LayerNorm(\mathbf {Z}^{^{\prime }}_{l})) + \mathbf {Z}^{^{\prime }}_{l}, \) 
